var total = 31;
if (total >= 30)
{
total -=20;
}
else
	total +=20
console.log(total);

var year = 2005;
if (year%4 === 0 && year%100 !=0 ||year%400 === 0)
{
	console.log("闰年")
}
	else
	console.log("不是闰年");

var x = "";
w=!x;
console.log(w);
if (w)
{
console.log(x = "这家伙很懒，什么也没有留下")
};
  console.log(x,typeof x);

  var a = 5<1 || 62;
  console.log(a);

  var userName = "ma";
  var res = userName || "游客";
  console.log(typeof userName);
  console.log(res);
